1. Field of the Invention:
The present invention relates to a method and apparatus for lining pipe lines, especially those buried in the ground, such as gas conduits, city water pipe lines, sewage pipe lines, oil pipe lines, construction pipe lines like power transmission wires or telecommunication cables, etc., suitably those having a large inner diameter, for the purpose of repair or reinforcing these pipe lines. More particularly, the present invention relates to a method and apparatus for lining such pipe lines, especially those buried in the grounds, which is so improved as to secure complete sealing of a pressure container for inserting the lining material into a pipe line while preventing a binder applied onto the inner surface of a tubular lining material from being squeezed backwards when the lining material is introduced into the pressure container.
2. Description of the Prior Arts:
A variety of methods utilizing the principle of evagination (or eversion) have been proposed from the past as a means for lining pipe lines with a tubular lining material. These pipe-lining methods which are generally called "evagination-lining" methods are carried out in such manner that a flexible lining material in the form of a tube previously provided on the inner surface thereof with a binder is inserted into a pipe line to be treated and is allowed to advance therein while turning the lining material inside out under fluid pressure whereby the lining material is bonded onto the inner surface of the pipe line by the aid of the binder. According to a pipe-lining method of this type, it is unnecessary to dig up a pipe line over its full length on application of a lining material thereto and the method is operable simply by forming manholes at both terminal ends of the pipe line to be treated. The pipe-lining work itself can be done within a short period of time even for a long pipe line and so these methods are now widely employed as an advantageous pipe-lining technique.
In these pipe-lining methods, a liquid such as water or a gas such as air is generally used as a fluid to be introduced under pressure into a pressure container to push a tubular lining material forward under evagination.
The method disclosed in Japanese Laid-open Patent Appln. No. Sho. 50-98984 (corres. to U.S. Pat. No. 4,064,211) is an example of the so-called evagination-lining methods wherein water is used as the fluid. According to this method as schematically shown in FIG. 5, one end of a tubular lining material provided on the inner surface thereof with a binder is annularly fastened in an evaginated state to one end of a pipe line to form a turning point of evagination and water is introduced into the interior of the lining material from the space opened in rear of the turning point of evagination whereby the lining material is allowed to advance within the pipe line by the pressure of water introduced while being turned inside out to attain lining of the pipe line. As shown in FIG. 4, a small tube is inserted into the pipe line and warmed water is circulated to accelerate curing of the binder. In this method wherein water is used for evagination of the lining material and warmed water is used for accelerate curing of the binder, a considerably large amount of water and warmed water is required in case of lining a long pipe line, and so the operation for evagination of the lining material and circulation of warmed water is extremely troublesome. In particular, it is difficult to bond the lining material completely onto the inner surface of the pipe line when the pipe line is inclined or bent in vertical direction. The pressure of water varies according to the height of the ground where the lining treatment is carried out; unnecessary high pressure is applied to the lining material when the ground is low so that there may be a fear of destroy of the lining material and/or pipe line. If the ground is high, on the other hand, the pressure of water becomes lower and, in the extreme case, even a negative pressure is exerted to the lining material so that the lining material once applied onto the pipe line is peeled off or may be collapsed by external pressure to clog the pipe line. Further, a tremendous operation is necessary for removal of a large amount of water used for evagination of the lining material and acceleration of curing the binder after completion of the lining treatment. In addition, residual water in the lining material after the pipe-lining treatment gives a bad influence on the heat efficiency of warmed water to be introduced in the subsequent step for accelerating curing of the binder so that a long period of time is needed for the curing of the binder. Thus, the evagination-lining methods wherein a liquid such as water is used for producing fluid pressure require troublesome operations which render these methods economically unattractive.
In case the fluid to be pressurized is a gas such as air, on the other hand, control of the fluid pressure as well as removal of the fluid after completion of the lining treatment is easy and technically preferable. In the methods disclosed in U.S. Pat. Nos. 4,368,091 and 4,334,943, for example, compressed air is usually used as the pressurized fluid for causing evagination. These methods enable control of the pressure of air required for evagination of the lining material by the aid of a pressure container, and concurrently adjustment of the amount of a binder to be applied onto the inner surface of the lining material inside or outside the pressure container. These methods, in particular, the method in the latter mentioned patent, are especially excellent along the existing pipe-lining methods in that the lining operation can be carried out, without forming any wrinkle on the lining material and forming any narrow path in bend portions of the pipe line, by adjusting the speed of the lining material in its advancing movement within the pipe line by the aid of a special evagination-inducing belt drawn from the opposite side of the pipe line. In such pipe-lining methods using compressed air as the pressurized fluid, however, a problem arises in sealing of the pressure container to prevent leakage of compressed air. In this case, compressed air is mechanically sealed at a slit of the pressure container through which a tubular lining material is fed in flattened state. To secure sealing of the pressure container for preventing leakage of compressed air, a sealing member at the slit has to be contacted under pressure with the lining material fed therethrough. In recent years, tubular lining materials are provided in the majority of cases with a binder prior to being transported to a place where the pipe-lining treatment is to be carried out. If a tubular lining material previously provided on the inner surface thereof with a binder is fed in flattened condition into the pressure container, the binder in the lining material is squeezed at the slit and partially remains in rear of the slit so that the lining material cannot be provided with a sufficient amount of the binder to weaken the bonding force between the lining material and the pipe line.
In Japanese Laid-open Patent Appln. No. Sho. 55-15852, there is disclosed a pipe-lining method wherein a tubular lining material previously provided in the inner surface thereof with a binder is fed through a slit 29 into a pressure container 6 having a simple structure (FIGS. 6 and 8). According to this method, a frictional resistance of the lining material at the slit 29 is so high that a high air pressure is required to perform evagination of the lining material. Further, the binder is strongly squeezed out at the slit 29 so that the lining material cannot be provided with a sufficient amount of the binder.
In Japanese Laid-open Patent Appln. No. Sho. 57-38114 (corres. to U.S. Pat. No. 4,427,480), there are disclosed a method and an apparatus for lining pipe lines according to the so-called evagination lining method, wherein a specific sealing device is used for the conveyance of a sufficient amount of a binder into the pressure container without being pushed back so that bonding of the lining material to the pipe line can be effected satisfactorily. According to this apparatus, the pressure container is provided with a special sealing device in place of a simple slit and this sealing device comprises a toothed drum rotatable on the path of a lining material provided in the inner surface thereof with a binder, a sealing member in close contact with the toothed drum to secure air-tightness and a squeezing base positioned beneath the toothed drum to support the lining material, and is operated in such manner that the lining material interposed between the rotating toothed drum and the squeezing base is squeezed in at least 2 positions at all times with the adjacent teeth on the drum lest the binder should be pushed back. The pressure container is mechanically sealed by this specific sealing device so that the lining material enclosing a sufficient amount of the binder can be inserted into a pipe line without the binder being pushed back. However, this apparatus still has some problems in actual use; the sealing device is complicate in structure and the sealing effect is not perfect so that the compressed air used a propellant for the lining material tends to leak out.
Under the above mentioned circumstances, there is still a great demand for developing a pipe-lining method wherein evagination of the lining material is carried out by using a compressed gas but all the problems mentioned above incidental to the use of a compressed gas are solved.